I'm fairly new to digital painting and this is basically my first laptop. I wanted to know basic things like how big a canvas should i start with and how big can/should I go. I wanted to start by working on simpler things on smaller canvases.Then when I really know what I'm doing, I'll use bigger canvases for when I want to make more detailed work. So, where do I start and what are some other things that I need to be aware of(dos and don'ts)? Also, I don't think my computer is that strong,I'll post my system info below.

Honestly, that processor may give you trouble with larger canvases which will be a problem. I'd reccomend going atleast 2k x 2k, as any smaller and the tools become rough/pixelated. I typically start a canvas at 4k x 4k then adjust the shape to my liking. I even do my sketches on this size canvas, the larger the canvas the more pixel space and the smoother your tools work. Think about your canvas as a grid with a bunch of tiny squares, the more squares the smoother a line will appear, and vice versa.

I agree with Snake', that Celeron is going to be a huge bottleneck, I used to have basically the same set up except my Celeron was clocked at 3.0ghz, but even then it was super slow. You're probably going to want to use a super light weight program like Paint Tool Sai with that rig. Also, I think you should always just use the largest canvas you can without any lag, it'll be different with every PC and program, so just experiment by scribbling on various canvas sizes. If you really want to draw small you can just zoom out, and that way if you decide you want to paint something you won't have a blurry mess due to resizing.

I see. As of now, this is the only pc I got and I'm gonna make the most of it. I use clip studio paint by the way. I'm going to start saving up for a new pc and I have no idea what to get. What do you all recommend?

To put it in perspective, my work PC I built was 2.6k after tax. But will last for years to come. You can build a really good desktop for around 1-1.5k. Highly reccomend a 1050ti graphics card if your on a budget.

I'd focus on high RAM(16GB+), multi-core CPUs with high clock speeds, and getting a secondary SSD(it doesn't need a ton of storage). The GPU doesn't do much for most painting programs other than GUI animation stuff like smooth zooms and rotations, and rendering videos and 3D models if your program has that feature. As long as you get a decent motherboard+CPU set up, you can always buy things over time instead of all at once as well.